Smoking could be banned in town and city centres if Mark Drakeford succeeds in his bid to become the next first minister.
The Welsh Labour leadership candidate has included the plan in his manifesto for the contest.
Mr Drakeford, considered to be the favourite to win the election, also wants to ban smoking in the outdoor areas of cafes and restaurants.
Currently smoking is banned in indoor public places.
It is also banned in cars where children are present. The ban is set to be extended to schools and hospitals next summer.
Ministers banned smoking in enclosed public places in 2007.
Mr Drakeford tried to legislate for a partial ban on e-cigarettes in 2016, but the law was binned after members of Plaid Cymru withdrew their support.
His manifesto proposes to “extend [the] smoking ban to outdoor areas of cafes and restaurants and city and town centres”.
“As Health Minister, Mr Drakeford led a crusade against vapers, and now he wants to hit smokers by a ludicrous ban on people lighting up in outdoor places such as cafes,” said UKIP assembly leader Gareth Bennett.
Other proposals in the manifesto, launched in Barry on Monday, include installing drinking fountains across Wales.
He said he would consider requiring all new homes to have fibre broadband connections.
Mr Drakeford’s document makes no specific mention of the M4 relief road – despite a decision looming on whether to go ahead with the scheme.
Instead, it says the government would “maintain our commitment to tackle congestion, particularly in areas such as on the A55 in north Wales, the A40 in mid and west Wales and the M4 in south Wales”.
“Being in power is an opportunity, not a right”, Mr Drakeford wrote.
“We must use every day we have, and every lever we have, to make Wales a more equal, fair and just society.”
Welsh city and town centre smoking ban proposed by Mark Drakeford}